Jonathan Koppenhaver, a mixed-martial-arts fighter known as War Machine, is accused of a savage beating of his ex-girlfriend in Las Vegas. (Las Vegas Police Department)

A California mixed-martial artist is now the prime suspect in a brutal Las Vegas assault that left his ex-girlfriend with 18 broken bones and a lacerated liver, according to police and a statement issued by the victim.

Jon Koppenhaver, a Simi Valley native who went by the nickname "War Machine" while competing for Ultimate Fighting Championship, allegedly pummeled his ex-girlfriend and an unidentified male early friday morning at her Las Vegas home.

Advertisement

Christy Mack, an adult film star who identified Koppenhaver as her ex-boyfriend, said he arrived at her home around 2 a.m. Friday and assaulted her friend before turning on her, according to a statement she released via Twitter.

On Tuesday, Las Vegas Police said they had issued a warrant for Koppenhaver's arrest, charging him with several counts of battery, assault with a deadly weapon and other crimes.

Mack posted several pictures showing her eyes swollen shut and purple and black bruises across her body, and in a statement, she claimed Koppenhaver forced her to shower in front of him, beat her savagely and assaulted her.

Mack said she suffered 18 broken bones, a fractured rib, a severely ruptured liver and leg injuries that left her unable to walk, according to the statement.

She also claimed Koppenhaver stabbed her several times, and that he had beaten her previously before ending the relationship in May.

Las Vegas Police did immediately offer comment on her description of events. Authorities also released a mugshot of Koppenhaver from a 2009 battery arrest, but did not offer further details.

Koppenhaver, 32, held a 6-2 fighting record within UFC and was a cast member for a season of "The Ultimate Fighter" reality TV show.

On Monday, he took to Twitter and said Mack's friend attacked him first, adding that he went to her house to propose marriage.

"I'm not a bad guy, I went to surprise my gf, help her set up her show and to give her an engagement ring and ended up fighting for my life," he wrote on Twitter.

He also seemed to suggest he was on the run from police because they would not give him "fair play." On Sunday, Koppenhaver also sent several messages to Mack.

"I just wanted to see your face when I surprised you with the ring ...this is a nightmare. You're in my thoughts," he wrote.

A native of Simi Valley, Koppenhaver described a troubled past during an interview he took part in while appearing on the UFC reality series. Koppenhaver said his mother battled drug addiction and he witnessed the death of his father, a retired Los Angeles police officer.

"I'm not a bad guy," he said in the interview. "I don't try to cause trouble."

Koppenhaver last fought for UFC in 2008, and his last professional fight was a loss at a Bellator event in October of 2013.